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Glossary of Terms

absolute address (AA) value

AA is a DMSII term that stands for absolute address. An absolute address value is an A Series WORD (48-bits in length). In the DATABridge Client, AA is the hexadecimal representation (12 character strings containing the characters 0–9 and A–F) of the AA value on the host. DATABridge Client uses the AA values to implement unique keys for the parent structures of embedded data set records. It also uses AA values to reference the records of data sets that do not have DMSII SETS with the NO DUPLICATES ALLOWED attribute.

AA values are not constant. Any DMSII reorganization (record conversion, file format, or garbage collection) changes these values.

Note: DATABridge Client supports numeric AA values that are stored as NUMBER(15) in Oracle, BIGINT in SQL Server, and DECIMAL(15) in DB2.

Accessroutines

The Accessroutines program is a DMSII library program that controls access to the database, reads and writes records, and creates the audit trail.

audit file

An audit file is created by DMSII and contains the raw format of changes made to the DMSII database by update programs. Audit file records contain the deletes, adds, and modifies that were made to the various structures. It can contain, for example, hours, days, or weeks worth of information.

When an audit file is closed, DMSII creates the next one in the series. Audit files are closed for several reasons, including the following:

  • An operator closes the audit file with the mixnumberSM AUDIT CLOSE command
  • The audit file reaches the file size set in its DASDL
  • There is an I/O error on the audit file
  • There is not enough disk space for this audit file
  • The database update level changes due to database definition changes
  • A DATABridge accessory closed the file in preparation for the fixup phase after extracting records from a DMSII database
  • The current audit file could not be found
  • A file reorganization was executed to modify the DMSII structure

DATABridge uses the audit file for the raw data of each database change to exactly replicate the primary database. DATABridge records the audit location (AFN, ABSN, SEG, IDX) between runs, so it can restart without losing any records.

If you have DATABridge Plus or you set the DBEngine Read Active Audit option, DATABridge can access the current audit file. If you do not have DATABridge Plus, and you do not set Read Active Audit = true in the DBEngine parameter file, DATABridge can access audit information up to and including the current audit file minus one. Additionally, the audit file contains the update level at the time the audit file was created. The update level in the audit file and the update level in the DESCRIPTION file used by DATABridge must match before DATABridge will update a replicated database.

audit trail

The audit trail contains all of the audit files generated for a database. The DATABridge Engine reads the audit files to extract updates. It then passes the updates to the Client to be applied to the relational database. After the updates have been successfully extracted, the Client saves the state information, which includes the location in the audit trail from which the last group of updates for the data set were read.

caching

A process that filters files before they're requested by the DATABridge Client. Caching allows DATABridge Enterprise Server to send Client data requests quickly and without placing an additional resource burden on the mainframe.

client

The client is the computer system that will receive DMSII records from the primary database. The client could be a Windows computer, a UNIX computer, or an MCP server. The client can have a relational or a DMSII database.

cloning

Cloning is the one-time process of generating a complete snapshot of a data set to another file. Cloning creates a static picture of a dynamic database. DATABridge uses the DMSII data sets and the audit trail to ensure that the cloned data represents a synchronized snapshot of the data sets at a quiet point, even though other programs may be updating the database concurrently. DATABridge clones only those data sets you specify.

Cloning is one phase of the database replication process. The other phase is tracking (or updating), which is the integration of database changes since the cloning.

consolidated file

A file created by DATABridge Span that contains all replicated records from various data sets.

CONTROL file

The DMSII CONTROL file is the runtime analog of the DESCRIPTION file. The DESCRIPTION file is updated only when you compile a modified DASDL. The CONTROL file controls database interlock. It stores audit control information and verifies that all database data files are compatible by checking the database timestamp, version timestamp, and update level. The CONTROL file is updated each time anyone opens the database for updates. The CONTROL file contains timestamps for each data set (when the data set was defined, when the data set was updated). It contains parameters such as how much memory the Accessroutines can use and titles of software such as the DMSUPPORT library (DMSUPPORT/databasename).

DATABridge uses the CONTROL file for the following information:

  • Timestamps
  • INDEPENDENTRANS option
  • AFN for the current audit file and ABSN for the current audit block
  • Data set pack names
  • Audit file pack name
  • Database user code
DASDL

Data and Structure Definition Language (DASDL) is the language that defines DMSII databases. The DASDL must be compiled to create a DESCRIPTION file.

data set

A file (structure) in DMSII in which records are stored. It is similar to a table in a relational database. You can select the data sets you want to store in your replicated database.

DATABridge Director

DATABridge Director is a Windows Service installed with Enterprise Server that starts Enterprise Server whenever a data request is received.

When you start your computer, Director starts and reads the ListenPort registry value to determine which TCP/IP port communicates with DATABridge Clients.

DATABridge Plus

DATABridge Plus is an optional program that enables DATABridge to access and retrieve information from the current audit file. If you have not set Read Active Audit = true, the most recent audit file DATABridge can read is the current audit file minus one. For example, if the current audit file number is 23, DATABridge can access audit file number 22 (23 - 1).

DBClient

A Client program that is launched by the service. DBClient handles the processing of DMSII data and updates the same as dbutility, except that it runs as a background run and uses the Client Console to display its output and interact with the operator.

DBClntCfgServer

A program that handles all requests from the Client Console specific to a data source. These requests include updating the client configuration file, providing access to the client control tables, and handling the Client Configurator. Like DBClient, this program is run by the service as a background run.

DBGenFormat

A host utility that creates translation, filter, and format routines. The GenFormat utility interprets the GenFormat parameter file to generate ALGOL source code patches, which are included in a tailored support library (a customized version of the DATABridge Support Library).

DESCRIPTION file

The DESCRIPTION file contains the structural characteristics of a databases (physically and logically). It is created from the DASDL source by the DASDL compiler and contains the layout (physical description), timestamp, audit file size, update level, logical database definition, and any static information about the database. It contains information about the database, not the data itself.

There is only one current DESCRIPTION file for each DMSII database. DATABridge must have access to the DESCRIPTION file before it can replicate a database. Additionally, DATABridge uses the DESCRIPTION file information for consistency checks between the primary database and the secondary or replicated database.

The DESCRIPTION file corresponds to the schema in a relational database.

direct disk

A cloning method that allows DATABridge Enterprise Server to clone and update DMSII data sets without using any significant mainframe resources. Direct disk cloning requires a SAN (Storage Area Network) or Logical Disks configured to make MCP disks visible in Windows.

entry point

A procedure in a library object.

extraction

The process of reading through a data set sequentially and writing those records to a file (either a secondary database or flat file).

file format conversion

A DMSII file format conversion affects file size values (for example, AREASIZE, BLOCKSIZE, or TABLESIZE), but it does not change the layout of the records in a DMSII database.

filler substitution

A DMSII filler substitution is a technique for avoiding a reorganization. It changes record layouts, but does not move records around.

garbage collection reorganization

A garbage collection reorganization moves records around, but it doesn’t change the layout of the DMSII database. Its primary function is to improve disk and/or I/O efficiency by eliminating the space occupied by deleted records. Optionally, a garbage collection reorganization reorders the remaining records in the same sequence as one of the sets.

lag time

The lag time is defined as the elapsed time between the time a record in the DMSII database is updated and the time where this update appears in the relational database. This value accounts for any difference between the clock on the mainframe and that on the client machine.

mutex

A mutex is an operating resource that is used to implement a critical section.

null value

The value defined in the DASDL to be NULL for that ALPHA data item. If the DASDL does not explicitly specify a NULL value for a data item, the NULL value is all bits turned on.

primary database

This is the original DMSII database that resides on the host. DATABridge replicates from the primary database to one or more client databases. The client databases can be another DMSII database or one of several relational databases. Compare this to the replicated (or secondary) database.

quiet point (QPT)

A point in the audit trail when the DMSII database is quiet and no program is in transaction state. This can occur naturally, or it can be forced by a DMSII sync point.

record format conversion

A DMSII record format conversion occurs when a data set or set (group of keys) is reordered or reformatted. It indicates that changes were made to a data set format, or to data items, such as changing the length of an item, for example, BANK-ID NUMBER (10) to BANK-ID NUMBER (15).

record serial number (RSN)

Record sequence numbers (RSN) are 48-bit quantities used by the DATABridge Engine in the case of DMSII XE. RSNs will always be used instead of AA values. RSNs are always valid; they will not change after a garbage collection reorganization.

replicated database

The replicated database is the database that resides on the client and contains all of the records cloned from the DMSII database that you specified for cloning. The replicated database is updated periodically with changes made to the primary (original) DMSII database. The periodic update (or tracking process) is explained later in this section. Compare this to the primary database.

replication

The ongoing process of cloning and tracking a DMSII database.

secondary database

The replicated database. The replicated database is the database that resides on the client and contains all of the records cloned from the DMSII database that you specified for cloning. The replicated database is updated periodically with changes made to the primary (original) DMSII database. The periodic update (or tracking process) is explained later in this section. Compare this to the primary database.

semaphore

Operating system resources that are mainly used to implement thread synchronization.

service

A service (Windows) or daemon (UNIX) that automates most Client operations from the Client Console. It handles scheduling for the Client and messaging to the Client Console.

set

An index into a data set. A set has an entry (key + pointer) for every record in the data set.

structure

A data set, set, subset, access, or remap. Each structure has a unique number called the structure number.

subset

An index into a data set. A subset does not necessarily have an entry (key + pointer) for every record in the data set. Subsets are used to access selected members of a data set and to represent relationships between data set records. Subsets typically contain fewer entries than normal sets.

An automatic subset is any subset that contains a WHERE clause and is maintained by DMSII.

A manual subset is any subset that is maintained by an application.

table

A data structure in the client database corresponding to a data set or remap in the host DMSII database.

tracking

Tracking is an ongoing process for propagating changes made to records in the DMSII primary database to the replicated database. The DATABridge Span accessory and the DATABridge Server Accessory perform extraction as well as tracking.

Tracking is one phase of the database replication process. The other phase is cloning.

undigits

A NUMBER data item containing bit values from 10 to 15 in one or more digits. The digits in a NUMBER data item should contain values from 0 to 9; however, it is possible for the digits in NUMBER data item to contain values 0 to 15. Because values 10 to 15 are not valid digit values, the digits in NUMBER data items containing values from 10 to 15 are called undigits.